Myth: People Use Only 10 Percent of Their Brains

You’ve certainly heard it: Humans use only 10 percent of their brains, but there is no scientific basis for this assertion. The origins of this myth are obscure. Some researchers have traced the idea to misattributions of the words of Albert Einstein, Dale Carnegie, or William James (a Harvard psychologist). Others use the following to bolster the idea:

The fact that some people who, through some developmental injury or anomaly, have brains 10 percent the size of the average adult human but appear normal. The fact that the brain can developmentally correct for some such injury or anomaly doesn’t mean that these people’s brains and functionality are completely equivalent to those with non-injured brains. Nor does it mean that all the neurons in non-injured brains aren’t actually used.

The existence of savants, people with extraordinary calculating or artistic skills that seem beyond normal human capability. The idea here is that savants use some percentage of the brain for these skills that others don’t. That may be the case, but most savants show profound disabilities in other areas. So how would you equate the novel ability to memorize phone books while simultaneously being unable to conduct many normal life functions such as dressing oneself with the idea that savants use more of their brains than people who don’t possess extraordinary ability in any particular area but who engage in full and meaningful lives?

The assertion that people use only 10 percent of their brains is not only untrue, but meaningless. Consider what it would mean if the statement were true: You could remove 90 percent of your brain with no noticeable difference.

This is certainly not the case. Every known case of such extensive brain damage shows profound incapacity.

Or maybe you could kill 90 percent of the neurons throughout the brain with no effect if you killed only the redundant ones. Although an interesting idea, it’s currently technically impossible to test. There is no way, therefore, to assert the truth of the statement from any evidence, or to determine whether the percent you really use is 20 percent, 89 percent, or anything else.

You can’t simply count neurons to estimate level of function. For example, by some estimates, the cerebellum has as many neurons as the entire rest of the nervous system, but if the cerebellum is destroyed, the primary result is people who are somewhat clumsy and have slightly slurred speech. The fact that you can function without a cerebellum doesn’t mean you don’t “use” the neurons in it when you have one.

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